1. Field of the Invention
The present invention relates to a film forming pre-treatment method and a semiconductor device manufacturing method and, more particularly, a film forming pre-treatment method used when silicon containing insulating film, etc. are to be formed by thermal CVD method on a substrate on which interconnection layers, etc. are formed and a semiconductor device manufacturing method employing the film forming pre-treatment method.
2. Description of the Prior Art
In the prior art, in the middle of manufacturing process of the semiconductor device, the SiO.sub.2 film is to be formed on the wafer by thermal reaction at atmospheric pressure or low pressure while using the reaction gas including TEOS representative of organic silane and ozone representative of oxygen containing gas. In such case, it has been well known that remarkably abnormal results are caused during or after film-forming process if a deposited surface is contaminated by foreign material, etc. For the purposes of example, there have been detected reduction in film forming rate, formation of porous film, reduction in etching rate of the film, abnormal shapes of the film shown in FIGS. 1A to 1E, etc.
Where film forming conditions are subject to the influence of surface condition of the substrate is called "surface dependency" in film formation by the CVD method. Factors which exert a bad influence upon film formation by CVD method using the reaction gas including organic silane and ozone, include absorption of moisture to the surface, charging, uneven distribution of charging which is ready to occur if the conductive film and the insulating film are mixedly formed, residue of organic matter or nitride such as resist residual, metallic contamination, etc.
In order to suppress such surface dependency, countermeasures have been taken as follows. In other words, in a flowchart in FIG. 2 including routines (A) and (B) and illustrating various processes from film forming pre-treatment to termination of film formation,
1) the deposited surface is covered in advance with an insulating film formed by making use of low concentration ozone as oxygen containing gas, as shown in the routine (A), to thus shield from surface contamination, or PA1 2) the deposited surface is covered previously with an insulating film formed by plasma CVD method (PECVD method), as shown in the routine (B), to thus shield from surface contamination.
Meanwhile, according to the above countermeasures, plasma irradiation process and coating of the insulating film formed by plasma CVD method are especially effective. However, if the surface has been contaminated to a considerable extent, such countermeasures fail to remove contamination of the ground surface sufficiently so that influence of such contamination cannot be suppressed sufficiently.
In this case, upon coating the insulating film by of plasma CVD method, surface dependency can be suppressed to a considerable level if the thickness of the insulating film is increased. But such thicker insulating film is not suited to current trends demanding miniaturization of the semiconductor device and therefore a thickness of the insulating film is made as thin as possible. In addition, if unevenly distributed charges exist on the surface, this countermeasure fails to shield from contamination by means of coating of the insulating film and as a result, abnormal film formation cannot be prevented.